The invention relates to a wind turbine comprising a tower, a nacelle rotatably arranged on the tower, and a helicopter landing pad arranged on the nacelle.
Besides erecting wind turbines in offshore areas, it is also the maintenance of offshore wind turbines that places high demands on the safety of the personnel maintaining the offshore wind turbines and on the logistics for carrying out such tasks. The offshore areas in which wind turbines can be usefully erected are at the same time areas with wind speeds that on annual average are high, changeable weather situations and high waves and are thus areas that under extreme conditions are only hardly accessible or not accessible at all.
The necessity, that exists for economic reasons, to keep the downtimes of wind turbines as short as possible, is thus in competition with the possibility, in the maintenance or repair case of an offshore wind turbine, to reach the offshore wind turbine at all. It is in particular also the time for this that has to be taken into account due to the decentralised location of such wind turbines, which is required to reach the offshore wind turbines from the mainland. Over and above this, the repair case of a wind turbine regularly also coincides with extreme weather that permits access to the wind turbine in need of repair only during very short time windows, if at all.
Therefore several devices of an offshore wind turbine have been proposed to safely transfer personnel and material by air or by water above the water surface and also below the water surface to a plant in need of maintenance.
Despite the fact that the trip to an offshore wind turbine below the water surface by means of a submarine, as has been proposed for example in DE 10 2005 055 585 A1, is largely independent of the weather, this method is very time consuming and necessitates especially designed underwater vehicles for docking to the offshore wind turbine.
Of the two types of transport mentioned above the water surface, it is again the transport of material and/or personnel using a helicopter that is preferred since for the outward and return trips less time has to be planned compared to travel by ship. In particular in the case of rapidly changing weather, (the time for) the transport by ship can hardly be calculated.
In particular during transport by helicopter it is advantageous if the personnel can be directly set down on the nacelle of the wind turbine since there is a need for the personnel, for maintenance purposes, to climb the tower to the nacelle and thus the downtime of the plant in need of maintenance can be kept short.
For setting down the personnel from a helicopter on a wind turbine, for example upwardly open cage structures, so-called hoisting platforms, arranged for example on the nacelle of the wind turbine, are known into which the personnel can be lowered by means of a winch from a helicopter. However, this procedure of lowering personnel from a helicopter hovering above the wind turbine, demands increased attention by the pilot, the helicopter personnel operating the winch, and the maintenance personnel that is hooked in on the cable of the winch and is to be lowered on the wind turbine, which in addition must have particular qualification. In addition, this procedure is also inconvenient and not without risk for all taking part in the procedure.
As an alternative to this, helicopter landing pads have already been disclosed that are supported on the tower and/or on the nacelle of the wind turbine; see also DE 100 13 442 C1 or DE 202 05 396 U1. The advantage of helicopter landing pads arranged on the wind turbine consists in the fact that the pilot does not have to stop the helicopter above the wind turbine and that it is easy and convenient for the personnel to exit the helicopter without any additional safety risk existing for the personnel as a result of the abseiling manoeuvre. In addition, it is also possible to save on fuel since the helicopter does not have to return to its base or have to circle in the area of the wind turbine but can be parked directly on the wind turbine for the maintenance period. In the case of a technician being injured during maintenance work it is also possible for him to be transported away much more easily.
However, the disadvantage of helicopter landing pads directly arranged on the wind turbine is that the landing pads essentially have to be arranged at the level of the nacelle opposite the rotor and thus as far away possible from the hub and the rotor blades of the wind turbine so that no collision of the rotor blades of the helicopter with the rotor blades of the wind turbine occurs. Minimum distances are stipulated for this. However, this arrangement requires the design of the supporting components to be of large dimensions for introducing the weight of the helicopter landing pad and the loads arranged thereon into the tower of the wind turbine, this design again increasing the entire weight of the wind turbine, the amount of work involved during the construction of the individual components and their costs.